This invention relates generally to devices and systems for mixing and dispensing multicomponent curable compositions, such as adhesives or sealants of the type formed by mixture of dual flowable components mixed together in a prescribed ratio. More particularly, this invention relates to an improved dispenser gun for use in controlled mixing and dispensing of such multicomponent materials, wherein the dispenser gun has a significantly improved and highly compact geometry for facilitated manual handling during dispensing procedures, and further wherein the dispenser gun is equipped with means for preventing undesired drool or dripping of the mixed components when dispensing is interrupted.
Dispensing devices are relatively well known in the art for use in mixing and dispensing flowable dual component materials such as adhesives and sealants and the like. Such devices typically include means for pumping separate flowable components such as polymerizable base and accelerator materials in a prescribed ratio through an internally vaned mixing nozzle. The mixing nozzle is designed to intermix the components in a thorough manner as the components flow to and are dispensed from a nozzle tip. The mixed components are normally selected to set up or harden to a nonflowable state in a relatively short period of time after dispensing, referred to frequently as the "cure" time. Examples of such dual component compositions include polymerizable resins and the like which react chemically when mixed, such as a polysulfide resin material adapted to be mixed with a polymerization initiator such as an appropriate oxidizer. Alternately, mixed dual components may be used wherein hardening of the components is controlled and/or speeded upon exposure to elevated temperature. The specific type of flowable components and their mixing ratio can be varied widely such that the mixed composition will cure with a desired set of physical properties.
Curable compositions of this general type are widely used in many different industrial applications wherein the mixed components are applied through the nozzle tip directly to the desired surface or point of application on an industrial product. In this regard, in a typical assembly line environment, the nozzle tip must be manipulated by a worker to apply the mixed composition in an intermittent manner to a succession of production items, with the dispensing device including means for interruption of composition flow as the nozzle is moved from one production item to another.
In the past, a variety of dispensing systems and related dispensing devices have been proposed for use in mixing and dispensing dual component compositions. For example, as described in U.S. Pat. Nos. 3,767,085 and 3,989,228, relatively lightweight dispenser guns have been developed for mixing and dispensing dual components contained within a convenient dual barrel cartridge which can be discarded when empty. Such dispenser guns have typically included manually operated ratchet mechanisms and the like for applying pressure to one or more pistons acting endwise upon the cartridge barrels to force the cartridge contents through a common mixing nozzle. Alternative designs have utilized power drive mechanisms such as a pneumatic piston unit for power dispensing of the mixed composition. In either case, the dispenser gun has exhibited a substantial length due to the endwise mounting of the cartridge and dispensing mechanisms. As a result, such dispenser guns have been cumbersome, and/or have required significant manual effort for operation. Moreover, such dispensing guns have demonstrated an extremely annoying tendency to drool or dribble a small amount of the mixed composition when the dispensing pressure applied to the cartridge has been relieved with the intent of halting composition flow.
There exists, therefore, a significant need for further improvements in dispenser guns of the type designed for dispensing mixed components of a curable composition or the like, particularly wherein the improved device is compact, lightweight, and relatively well balanced for easy manual handling while providing power driven dispensing, and further wherein undesired drool of the mixed composition is substantially prevented between successive dispensing steps. The present invention fulfills these needs and provides further related advantages.